While in Ipsen's Castle, weapons will do more damage the lower their attack power is. Weak weapons are sold by a local moogle, and the characters' default weapons can be found in many of the treasure chests. The unusual set-up does not extend to armor, add-ons or magic.

Due to steep, canyon-like walls that surround the castle, it can only be accessed with a chocobo or by airship. It is possible to develop Choco as far as dark blue (ocean/mountain crossing) by the time the party first visits the Forgotten Continent, so it is possible to visit Ipsen's Castle before it is mentioned in the story. If the party does so, however, the castle appears on the map as simply "?", and although it can be entered the castle is surrounded with a thick Mist and the front door is closed.

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Ipsen and his good friend Colin worked at a tavern in Treno. One day, Ipsen got a letter. The letter was so wet from rain that most of the writing was illegible. The only part he could read said, 'Come back home'. Nowadays, we have airships and stuff, but back then, it was really hard to travel. He didn't know why he had to go back, but he got some time off, gathered his things, and set out on his journey home. He walked a thousand leagues through the Mist. Sometimes he was attacked by vicious monsters, but he made it, because his friend Colin was by his side. And then, after much time on the road, he had to ask Colin something:"Why did you come with me?""Only because I wanted to go with you."

According to the Final Fantasy IX Ultimania, Ipsen's Castle is one of the locations from Terra that ended up on Gaia5000 years ago due to Garland's failed attempt to merge the two planets into one. The origin from Terra is made clear by the unusual-looking treasure chests, as Terran treasures are blue, whereas Gaian chests are wooden.

The castle is named after the explorer Ipsen, who is thought to be the first to discover the castle. Another etymological origin derives from Latin where ipse means it/her/himself, so as Lady Hilda decides on the castle's name, she means it will be called the "no name castle"—the "ipsen" castle (literally translated: the castle itself).

The four mirrors.

When the party is sent to Ipsen's Castle to retrieve the four elemental mirrors Amarant challenges Zidane to a race, saying that he "works alone". The party ventures through the maze-like interior, made all the more confusing due to the castle's mirrored structure. Amarant wins and vacates the premises after declaring his disbandment from the party. Zidane and his friends collect the mirrors, but are interrupted by the monster, Taharka, the mirrors' guardian.

Upon exiting the castle, the party discovers Amarant hasn't come out yet. Zidane scours the castle and finds and rescues him. When the two return, Zidane formulates a plan to raid the four elemental shrines, whose locations are marked by the mirrors' placement on the mural they were found in.

Kumool at Ipsen's Castle receives a letter from Mogki from Lindblum Castle:

Where is Mognet Central?

From Mogki to Kumool

Hey, Kumool. How are you, kupo?
Us moogles in Lindblum are all wondering
the same thing, these days:
Where the heck is Mognet Central?
No one knows, kupo.
Do you know where it is, Kumool?
It's supposedly very far away, and you
can't enter very easily, kupo...

After the party returns from Terra they can start a side quest to fix Mognet Central by talking to Kupo in Alexandria. As part of this chain of correspondence Mogryo from Black Mage Village sends a letter to Kumool:

Rare Item

From Mogryo to Kumool

I heard that the machine in Mognet Central
broke down! It's because they're missing
that item!

I wonder where you can find one? Kupo?
It's a rare item, so I don't think
you'll find one very easily...

To obtain Ancient Aroma the player must solve the puzzle of the rotating tablet near the elevator to the mirror room. When prompted, Zidane is required to examine, push, pound, think, push, think, try something drastic, and rest to flip the wall and gain access to a new area. This opens up a door in the dungeon's entry foyer, directly to the left of the first door the party entered. The new passage leads to a large glowing sword with three ledges and two pots.

A voice within the room whispers, Fight the flow of time, implying the pots must be picked up and placed on the next ledge counterclockwise from its present location. After both pots are rotated thrice, the electricity within the blade will fill one pot, from which the Ancient Aroma may be collected.

If, instead of going to Ipsen's Castle by airship (as part of the story), the player goes there by gold chocobo, upon leaving the dungeon, the chocobo will be replaced by the party's airship.

After the battle with Taharka, on the way out of the castle, a cutscene will play showing one of the non-Zidane party members nearly falling into a trapdoor, a result of having unknowingly triggered some traps in the castle. The member who barely avoids this peril depends on the player's party and the characters' priority over one another. If the party contains Garnet, then she will nearly fall into the trap. If she is not in the party, then Eiko will nearly fall into the trap. If neither Garnet nor Eiko is in the party, then Vivi will nearly fall into the trap. Finally, if Garnet, Eiko, and Vivi are all left outside of the castle, then Quina will nearly fall into the trap. Only Steiner and Freya are guaranteed not to have this peril, as is Amarant, who is not available to the player.

After the events of this location, Amarant, who, up to this point has gone without posing at the end of battles, will finally begin to perform a victory pose.

If the player attempts to leave the castle before meeting Amarant, Zidane will comment "I can't leave until I've finished my game with Amarant," and "I'm gonna find it before him." If Amarant has been found, but the party has not yet examined the mirrors, he'll comment "I gotta find out how to reach Terra before we leave here... I should look around some more." Finally, when playing with Zidane alone as he looks for Amarant, exiting will result in him stating "...Wait. I haven't found what I'm looking for. Where is he?"